Free HTML check
Email preheader checker
The grey line after the subject. Paste the HTML, or type the subject and preheader if you do not have the file yet.
Report
The report lands here.
Paste one email. You get the clip size, the inbox line, and which addresses do not open.
Inbox
Phone
Addresses
Show the rendered email
Your HTML in a frame. Not a screenshot from Gmail or Outlook.
EmailStitch runs this kind of check on the compiled file, once per translation.
The inbox writes this line for you
There is no preheader header in an email. Gmail, Apple Mail, and Outlook take the first text in the HTML. If you do not set that text, they use whatever comes first: “View in browser”, an image alt, or a navigation link.
The usual fix is a hidden line at the top of the body. A div with display:none, max-height:0, and overflow:hidden. The inbox still reads it. The opened email does not show it. This checker looks for that element, and for a class named preheader.
How much of it anyone sees
A phone shows about the first 40 characters. A desktop inbox shows about 90. This page cuts the preview there so you can see the cutoff before you send. Front-load the detail. A 140-character preheader is a paragraph the reader will not get.
The preheader sits on the same row as the subject. Repeating the subject wastes the only second line you have. Add the fact the subject left out: the date, the number, the thing in the email.
Paste the file when you have it
Typing the preheader shows the length. Pasting the HTML shows what the inbox will actually pick up, including a view-in-browser link that leaked into first place. If both are filled and they disagree, the file wins. That is what the client will read.
A spacer made of and ‌ after the real preheader is ignored. Those characters exist so the body copy does not trail into the preview. They are not the preview.
Questions
What is a preheader?
It is the preview text after the subject in the inbox list. It is not a header field. Mail apps take it from the first text in the HTML, unless you add a hidden line to control it.
How long should an email preheader be?
About 40 to 90 characters. The first 40 are what a phone shows. Desktop shows closer to 90. Put the useful part in the first 40, and do not repeat the subject.
Why does my inbox show “View in browser”?
That link is the first text in the HTML, and there is no hidden preheader before it. Move a hidden preheader above it, or the inbox will keep using the link.
- Email template testerPaste the HTML. This checker tells you what will go wrong before you send: size, preheader, unsubscribe, links, and alt text.
- Gmail clipping checkerPaste the HTML. If it is over 102,000 bytes, Gmail hides the rest of the message behind “View entire message”.
- Unsubscribe checkerPaste the HTML. A word in the footer is not enough. The link has to go somewhere, or the file has to carry your ESP’s tag.